The present invention relates to thermal management equipment and methods for computer memory modules, and more particular to a heat spreader that can be assembled with a memory module to promote natural convection cooling of the module.
Memory bandwidth requirements have steadily increased as a countermeasure against data starvation of central processors of personal computers. A number of different strategies have been employed to provide better data throughput to and from the system memory pool. The three most important measures have been to increase the memory clock frequency, increase the data rate, and increase the number of physical banks to allow for more pages that can be held open.
As a rule of thumb, power consumption of any integrated circuit increases in a linear fashion with the clock frequency and, therefore, the migration to higher memory core frequencies necessarily results in higher power draw. Likewise, the increased power consumption of open memory pages is well documented. Combined, the higher operating frequency, along with the increased system memory density and higher number of ranks/open pages, have reached a stage where heat dissipation of computer memory modules becomes a limiting factor. For example, in high density DDR2 SDRAM (double-data-rate two synchronous dynamic random access memory) components, a new access latency has been introduced to add wait cycles between bank-interleaved read accesses during the four bank activation window (tFAW), without which the memory components might incur thermal runaway.
Recently, thermal management of memory modules has employed dedicated memory heat spreaders that are added to the modules and serve the purpose of thermally buffering and dissipating the heat generated by the memory IC's. Typically, heat spreaders have been designed to have a solid surface for maximum contact with the individual components. However, a major drawback of such a configuration is that the heat spreader encapsulates the modules and traps the air space between the components. This trapping of heat does not affect the short term buffering of thermal transients by the heat spreaders, but raises the overall operating temperature of the modules.
The issue of heat trapping is especially of concern in the case of registered modules where a high speed clock chip or phase lock loop (PLL) chip and registers are added, either of which consumes constant power at a rate higher than that of the average memory IC. This has led to either overheating of the PLL and heating of the memory chips by the PLL.
In view of the heat-trapping problem, dedicated memory fans have been employed to reduce the dead air space between memory modules enclosed by solid-surface heat spreaders. While effective, fans incur an additional and undesirable cost. Other proposed solutions include the use of water-cooled memory modules that are more efficient, but are also more expensive to implement than fan cooling. In view of the above, there is a need for effective but less expensive cooling solutions for memory modules.